1. Field of the Invention
The present invention relates to a coating method using a plasma shock wave and a method for manufacturing a coated substance.
2. Description of Related Art
Heretofore, a laser peening method is used as a method using a plasma shock wave for reforming surfaces of such as machinery parts by applying residual stress into the surfaces.
Processing that uses the laser peening method is generally taken place by irradiating convergent laser beam to a surface to be worked, trapping produced plasma into a liquid medium such as water, oil, or the like, the liquid medium being formed on the surface to be worked, and applying a shock wave pressure generated thereby to the surface to be worked. Liquid such as water, oil, or the like for trapping plasma therein, needs to be formed on the surface to be worked so that the shock wave pressure generated by the plasma may be effectively applied to the surface to be worked.
Patent documents JP-A-2000-246468, JP-A-2006-122969 and JP-A-2007-169753 disclose a laser peening method in which liquid film such as water film or the like is formed on the surface to be worked so that plasma is trapped by the liquid film. Incidentally, according to the documents, a protection film such as black paint or the like is preliminarily applied to the surface to be worked. Moreover, a paragraph 0013 in patent document JP-A-2006-122969 discloses using running water as the water film.
Patent document JP-A-2002-346847 discloses a laser peening method, which is taken place with a laser radiation head and a surface to be worked being placed in the water (see paragraph 0004, FIGS. 10 and 11 in the document).
Moreover, the document discloses a peening method using a water-jet in combination with a laser (see the CLAIMS and FIG. 1 and so on).
Moreover, patent document JP-A-2007-169753 discloses a laser peening method in which a powder is struck into a surface to be worked by a shock wave of plasma generated when irradiating a laser.
According to the laser peening method, the powder is struck into the surface to be worked by irradiating the laser to a base sheet laid down on the surface to be worked, the base sheet preliminarily been made to carry the powder on one side thereof (see paragraphs 0040-0044 and FIG. 1 in the document JP-A-2007-169753). As a result, the surface to be worked in which the powder is implanted is obtained. In this way, reduction of slide friction and improvement of an antiwear characteristic are aimed (see paragraphs 0045-0046 and FIG. 2 in the document JP-A-2007-169753).
However, the technique disclosed in the patent document JP-A-2007-169753 is a technique, which is not for forming a coating but for implanting the powder sporadically into the surface to be worked. Moreover, equipments cannot help but being large-scaled because huge amount of energy is needed for implanting the powder (see paragraph 0043 and 0047 in the document).
As a coating technology, a thermal spraying including a flame spraying, a burst spraying, an electrical spraying such as an arc spraying and a plasma spraying or the like, a high-speed flame spraying (HVOF) or a cold spraying is used.